Testing Silicon, Automatically


The latest softwares identify chip-level test issues. Violations can even be analyzed by viewing directly on the circuit. Detailed violation information is available with context-sensitive help. These softwares also support full scan and partial scan test methodologies using mux-scan, clocked-scan, level sensitive scan design (LSSD). Support for designs with IEEE 1149.1/6 internal scan shifting protocols and related techniques are an additional plus.

Silicon Diagnostics

Post fabrication, you have a wafer, which has on it multiple die. Some of them are defective, while many are not. Identifying the defective parts is kind of a big deal. The good ones go to the market to be sold, whereas the defective ones are trashed.

In addition to identifying defective parts from manufacturing, test software can also isolate the location of defects on devices failing test patterns. Automatic and accurate defect isolation is an important step to diagnose critical yield issues, both during production ramp as well as in volume manufacturing. They also report the fault candidate locations that most likely explain the faulty device behavior observed on the tester. Current diagnostics use advanced heuristics and a high-performance fault simulator for rapid and reliable results in a volume manufacturing environment.

Plethora of tests: one little chip

DRC is just a broad way to cover the numerous checks a silicon die goes through before assembly and packaging. However, testing does not stop there. After testing, it again goes through tests to check for any errors in implementation and short circuits. I genuinely wonder if a silicon die passes more signal tests than circuit implementations.

I have a newfound respect for silicon

A piece of silicon goes through so much in it’s lifetime to get it right. Once it does get everything right, it either ends up in a lab or is implemented in a circuit by some manufacturer.

If it goes to the manufacturer, it’s alright. But if it ends up in a lab, it might end up with a rookie or the hands of a professor.

If the professor handles the silicon, it’s alright. But if it ends up with the rookie, they can either break it’s pins or handle it properly.

If they handle it properly, it’s alright. But if they break its pins, they can either throw it away, or tell the professor they broke it. Let’s be honest for a second, nobody tells the professor. It’ll be thrown away.